Rig mats have been used for many years to provide a level working surface over unstable and environmentally sensitive terrain for supporting the operation and movement of heavy equipment or vehicles thereon. A multiplicity of individual rig mats are typically arranged in an array, assembled on site, for forming a large working surface. The individual mats can be readily transported, used and reused for building temporary work surfaces of various desired dimensions.
As shown in FIG. 1A, a conventional rig mat consists of a generally rectangular planar steel frame having parallel sides and parallel mat ends. Rig mats are provided in a variety of sizes, however a common size includes a mat having a width of about 8 feet and sides having a length of about 40 feet. The frame encloses a grid of spaced apart, cross members, openings between which can be filled with panels of wood or composite materials. The panels sit in the openings, flush with a top working surface of the planar frame.
As shown in FIGS. 1B and 1C, each of the mat ends are typically configured with winching end structure to enable the connection of slings and the like for on-site manipulation, loading and unloading of the rig mats from transport trailers. The known winching structure comprises a pipe secured along the length of each mat end. Affixing the pipe is associated with significant material and labor cost to secure it to the rig mat. Mat ends are square and the pipe is round providing a difficult fabrication. As shown in FIG. 1B, the pipe extends along the mat end and a top flat bar or plate also extends along the mat end for welded connection to the mat end along one side and to the pipe along the parallel and opposing side. To secure the bottom of the pipe to the mat end, a plurality of gussets are welded periodically along the mat end and transverse of an axis of the pipe, extending between a lower quadrant of the pipe and the mat end. To further strengthen the connection between the pipe and the rig mat, a lower flat bar or plate is added as a lower brace, welded again at the pipe and at the mat end. The top plate, gussets and lower brace add to the cost of the rig mat module in material and labor. The lower brace, gussets and the top plate also increase the weight of the rig mat module. Further, the diameter of the pipe and the gussets also decrease the clearance beneath the pipe and a surface such as a trailer deck or ground, on which the rig mat module is supported. The reduced clearance makes it difficult for an operator to pass a winch cable around the winching ends for lifting and winching the rig mat modules. Accordingly when stacked on top of each other, conventional rig mats are separated by spacers to increase the clearance therebetween. Further, a spacer is sometimes also used between the mat and the ground to space the mat thereabove to increase the clearance therebetween. The process of adding spacers is labour intensive.
One known arrangement includes arranging rig mats end-to-end; arranging a winching end of one rig mat against a winching end of another rig mat. In the prior art, the two pipes of adjacent rig mats are abutted together, forming a nip, gap or a discontinuity formed therebetween. The discontinuity in the otherwise planar working surface can result in a safety hazard, increasing the likelihood for personnel to twist their ankles or trip.
There is a need for a rig mat which in addition to providing a rigid surface, ensures safety of personnel working on the rig mat, is economical, relatively lightweight and easy to assemble.